Toxoplasmosis and its Relationship with Various Mental Disorders

Toxoplasmosis is a globally distributed disease caused by a parasitic protozoan called Toxoplasma gondii (T. gondii) in humans and animals that often develops asymptomatic acquired infections but the important aspect of this parasitic infection is the possible risk of congenital transmission and its severe effects on the fetus such as hydrocephalus, microcephaly, deafness and abortion up to milder abnormalities such as psychomotor retardation, mental disability, hearing loss, slow growth, chorioretinitis, cryptogenic epilepsy and autism disorders in infants. The infection appears to be associated with neuropsychiatric disorders such as anxiety, schizophrenia, depression, weight loss, autoimmune thyroid disease, violence, and suicide attempts. The term Mental Disorders is used to refer to mental disorders that have behavioural or psychological symptoms which affect various aspects of life and cause anxiety. In this article, the possible association between this parasite and the major categories of disorders (based on the Diagnostic and Statistical Manual of Mental Disorders or DSM) is described. 1- Neurodevelopmental Disorders. The association of global developmental delay and communication disorders with toxoplasmosis has not been investigated nor the author has not found an article in this regard but some studies consider T. gondii to be an effective or ineffective factor in intellectual disability, autism spectrum disorder, attention-deficit hyperactivity disorder. 2- Bipolar and Related Disorders which seems people who were evaluated immediately after the onset of these mental disorders were more likely to be exposed to T. gondii. 3- Anxiety Disorders. In this group of diseases, toxoplasmosis association has not been investigated or the author has not found an article in this regard except in some studies which consider T. gondii to be an effective or ineffective factor in generalized anxiety disorder. Latent toxoplasmosis exacerbates anxiety and depression and can be a risk factor for mental illness, on the other hand, the results are varied for depression but the genetic background is important for the response to latent toxoplasmosis. 4- Trauma and Stressor-Related Disorders er. Toxoplasmosis association has not been investigated in this group nor the author has not found an article in this regard although there are studies that consider T. gondii to be an effective or ineffective factor in post-traumatic stress disorder. 5- Dissociative Disorders The association with toxoplasmosis has not been investigated or the author has not found an article on these subjects. 6- Somatic Symptom and Related Disorders include somatic symptom disorder, illness anxiety disorder, conversion disorder and factitious disorder which none of them has been studied concerning toxoplasmosis, or the author has not found an article on these subjects. 7- Feeding and Eating Disorder include anorexia nervosa, bulimia nervosa, rumination disorder, pica and binge-eating disorder which none of which has been studied with toxoplasmosis, or the author has not found an article about them. 8- Sleep-Wake Disorders include narcolepsy, insomnia disorder, hypersomnolence disorder, breathing-related sleep disorders, parasomnias and restless legs syndrome. Except for hypersomnolence disorder, and breathing-related sleep disorders which can be partly related to parasite infection, the rest of the diseases were not studied nor the author has not found an article about them. 9- Disruptive, Impulse-Control, and Conduct Disorders include kleptomania, pyromania, intermittent explosive disorder, conduct disorder and oppositional defiant disorder. Except for intermittent explosive disorder which can be partly related to parasite infection, the rest of the diseases were not studied nor the author has not found an article on these subjects. 10- Depressive Disorders. Except for major depressive disorder and persistent depressive disorder (dysthymia) which can be partly related to parasite infection, the rest of the diseases were not studied nor the author has not found an article on these subjects. 11- Substance-Related and Addictive Disorders. The association of this disease with toxoplasmosis has not been investigated nor the author has not found an article in this regard. 12- Neurocognitive Disorders include delirium and major and mild neurocognitive disorders. Apart from delirium, many articles have been published on the relationship between this parasite and major and mild neurocognitive disorders. 13- Schizophrenia Disorders include delusions, hallucinations and disorganized speech. Statistical analysis showed that among patients with schizophrenia and the incidence of latent toxoplasmosis may be a connection in incidence and latent toxoplasmosis appears to be a risk factor, especially for schizophrenia and anxiety. It seems that both schizophrenia and latent toxoplasmosis can inhibit neurotransmission, increase the production of L-quinoline and its neurotransmitters, hormonal imbalances, alter tissue regeneration processes, lack of fear, impair human cognition and reduce grey matter density. 14- Obsessive-Compulsive and Related Disorders Toxoplasmosis association has not been investigated in this group nor the author has not found an article in this regard although there are studies that consider T. gondii to be an effective or ineffective factor in OCD. 15- Personality Disorders include antisocial personality disorder, avoidant personality disorder, borderline personality disorder, dependent personality disorder, histrionic personality disorder, narcissistic personality disorder, obsessive-compulsive personality disorder, paranoid personality disorder, schizoid personality disorder and schizotypal personality disorder which none of them has been studied with toxoplasmosis, or the author has not found an article on these subjects. It seems that T. gondii can increase or cause some mental disorders and many articles have discussed the effect or lack of effect of this parasite also, the association of this parasite with a large number of diseases has not yet been worked out or needs further study. How and why this parasite affects the brain and nerves is still unknown to science that needs further investigation although it seems that infection with this protozoa may cause an increase or occurrence of some mental disorders.